RS25560 is a potent inhibitor of isolated rat and human DBH (dopamine B-hydroxylase) enzyme. Inhibition of this enzyme affects sympathetic tone by decreasing norepinephrine and increasing dopamine release from nerve terminals in response to sympathetic nerve stimulation. Since the elevated sympathetic tone in congestive heart failure is believed to contribute to the progression of the disease and to its poor prognosis, a DBH inhibitor has the potential for being a useful addition to the current pharmacologic treatment of this condition. The significance of this study is to provide a potential new therapy for the chronic treatment of congestive heart failure. This is the first study to evaluate RS-25560 in men who have been diagnosed with congestive heart failure, and is designed to determine the safety, tolerability, pharmacokinetics and pharmacodynamics of the compound in these patients. Each patient will be randomized to receive either an oral solution of suspension of RS25560, or matching placebo. If RS-25560 is found to be effective in men, the sponsor may conduct future studies in women with congestive heart failure.